1. Field of the Invention
The present invention relates to a data encoding/decoding method and related device capable of lowering signal power spectral density, and more particularly, to a data encoding/decoding method and related device capable of performing encoding mode switching without extra signal pins and performing dummy bit stuffing adaptively according to practical data pattern for lowering signal power spectral density of transmitted data.
2. Description of the Prior Art
With the advancement of the semiconductor technology, switching speed and efficiency of transistors are enhanced without end, such that data quantity capable of being processed every unit time by integrated circuit (IC) chips increases day by day. Thus, there should be an effective data transmission system for realizing data transmission among various kinds of IC chips. Currently, binary data transmission systems can roughly be divided into two kinds: One is to transmit data signals in the form of single-ended voltages, such as a transistor-transistor logic (TTL) interface, and the other is to transmit data signals in the form of double-ended differential voltages or currents, such as a low voltage differential signal (LVDS) interface, a reduced swing differential signal (RSDS) interface and a mini low voltage differential signal (mini-LVDS) Interface, etc.
Since digital data transmitted in the binary data transmission system alternates between 0 and 1, electronic signals carried on signal transmission lines of the binary data transmission system also swings up and down unceasingly. Thus, harmonics of the electronic signals existing on the signal transmission lines, which respectively belong to different frequency bands, are easily radiated in the form of electromagnetic waves through antenna effects of the data transmission system, resulting in that problems of electromagnetic Interference (EMI) and electromagnetic compatibility (EMC) can not be ignored. Therefore, in order to improve the above-mentioned problems, one general solution is to reduce the number of times that the transmitted data consecutively alternates between 0 and 1 as much as possible. However, in the prior arts, such doings often costs a lot of extra system expenses, for example, if encoding data being transmitted by a transition minimized differential signaling (TMDS) encoding method, two redundant bits (or called overheads) need to be padded into every 8 data bits being transmitted, and the number of the padded redundant bits cannot be adjusted adaptively according to data patterns of the transmitted data.
On the other hand, as a method disclosed in U.S. Pat. No. 6,628,256, extra signal pins are needed for indicating current encoding modes or status of the transmitted data. Thus, in this case, not only system costs are increased, but also safety requirements cannot be met since voltage swings of the extra signal pins are also easy to excite electromagnetic wave radiation.